松辽盆地南部梨树断陷混源油定量识别模式研究

Quantitative Identification Mode of Mixed Oil from Lishu Fault Depression in Southern Songliao Basin

生物标志物特征显示梨树断陷明显存在2种不同成因原油及其混源油。生物标志物质量分数与相对丰度变化特征表明三环萜烷、五环三萜烷和甾烷化合物参数均不适合梨树断陷混源油的定量判识,倍半萜参数能良好地展示混源油中混合比例的变化特征。利用C15重排/8β-补身烷参数的生物标志物质量分数配比计算的方法,计算了梨树断陷混源油中两类不同原油的混合比例,由此建立了梨树断陷混源油混合比例定量识别图版。根据图版识别的混源油混合比例,判断八屋地区混源油中来源于营城组下部烃源层的原油质量分数主要在2%～30%之间,原油层位越浅该类原油混合比例越高;七棵树和太平庄地区混源油中来源于营城组下部烃源层的原油质量分数分别在37%～60%和34%～50%之间。上述混合特征暗示梨树断陷混源油区西侧营城组下部烃源层来源油混入程度有限,东侧该类原油混入程度相对较高。上述混源分布特征为清晰认识梨树断陷不同类型原油的分布与运聚特征提供了有利证据。

Two different geneses of crude oils and mixed oils were demonstrated in Lishu Fault Depression by the characteristics of biomarkers.The characteristics of mass fraction and relative abundance of biomarkers showed that parameters of tricyclic terpanes,pentacyclic triterpenoid and steranes were not suitable for quantitative identification of mixed oils from Lishu Fault Depression,but oil mixing proportion changing characters of mixed oils could be well revealed by drimane.Based on calculation method of mixing proportion of C15 rearranged drimane /8β(H)-drimane,the mixing proportions of two types of crude oils in mixed oils from Lishu Fault Depression were calculated,and the quantitative identification chartboard of mixed oils from Lishu Fault Depression was established.According to the geochemical chartboard,it was judged that crude oils in the lower of Yingcheng Formation were among 2%~30% in Bawu Area,the lower the oil was,the higher the oil mixing proportion was,the crude oils among Qikeshu and Taipingzhuang Areas contained 37%~60% and 34%~50% respectively.It is suggested that the lower of oils in Yingcheng Formation are of small amounts in the west and of large amounts in the east of mixed oil area.The results provides strong evidences for understanding the distribution,migration and accumulation of different types of oils in Lishu Fault Depression.